Conventionally, projectors having a plurality of optical modulators respectively for modulating a plurality of color lights in accordance with image information, a color-combining optical element for combining the respective modulated color lights to form an optical image, and a projection lens for enlarging and projecting the formed optical image have been used.
In such projectors, a color-separating optical system such as a dichroic mirror separates a light beam irradiated by a light source into three color lights. Three optical modulators such as liquid crystal panels respectively modulate the color lights in accordance with the image information. The color-combining optical element such as a cross dichroic prism combines the modulated color lights to form an optical image. Finally, the projection lens enlarges and projects the optical image.
The respective optical modulators of such projectors have to be disposed at the back focus position of the projection lens. Further, in order to obtain a clearer image, pixel shift between the respective optical modulators and deviation in the distance from the projection lens have to be eliminated.
Accordingly, in manufacturing the projectors, a focus-adjusting process for accurately disposing the respective optical modulators at the back focus position of the projection lens and an alignment-adjusting process for aligning the pixels of the respective optical modulators are conducted with high accuracy. For instance, an optical device having optical modulators directly fixed on light-incident sides of a color-combining optical element after adjusting the positions of the optical modulators has been proposed (see Japanese Patent Laid-Open Publication No. 2000-221588).
In order to construct the optical device, a liquid crystal panel is accommodated in a holding frame having holes on four corners thereof, and pins with an adhesive being coated on the circumference thereof are inserted to the holes. Then, the ends of the pins and the light-incident side of the cross dichroic prism and the side of the pin and the hole of the holding frame are mutually adhered and fixed (so-called pin-spacer POP [Panel On Prism]). The material of the pins is an acrylic resin molded article.
In the above pin-spacer POP structure, an acrylic resin molded article is used for the pin component. Accordingly, the thermal expansion coefficient of the pin becomes higher than the holding frame or the color-combining optical element, so that a great thermal stress is generated at the boundaries of the respective components. Consequently, the thermal stress unstabilizes the connection between the pin and the holding frame or the color-combining optical element, so that a pixel shift on account of mutual position shift of the respective optical modulators fixed by the pin and position shift of the optical modulators relative to the back focus position of the projection lens are likely to be caused.
An object of the present invention is to overcome the above deficiencies and to provide an optical device and a projector capable of preventing the position shift of the optical modulators and forming a clear optical image.